Diepoxide from levopimaric acid transannular peroxide



3 463 769 DIEPoxrni: rnoli i rhvornuanrc ACID TRANSANNULAR PEROXIDEWalter H. Schulier and Ray V. Lawrence, Lake City, Fla, assignors to theUnited States of America as represented by the Secretary of AgricultureNo Drawing. Filed Apr. 2, 1964, Ser. No. 356,987

lint. Cl. C09f 1/04; C07d 1/10 US. Cl. 260--99 1 Claim A nonexclusive,irrevocable, royalty-free license in the invention herein described,throughout the world for all purposes of the United States Government,with the power to grant sublicenses for such purposes, is hereby grantedto the Government of the United States of America.

This invention relates to the new and useful diepoxide (I) and to itsesters and salts. More specifically, it relates to a process forpreparing (I) by means of the thermal rearrangement of 6,14-peroxy-A-dihydroabietic acid (II), by heating (II) in an inert solvent. Thediepoxide (I) have a variety of commercial uses including thepreparation of casting resins, laminating resins, adhesives, and can becombined with HA-type reagents to give surface coatings, as will bediscussed more fully below.

The structure of the diepoxide, sometimes referred to below as the freeacid, is (I):

It exhibits [a] 7O.3 (c. 0.80 in 95% ethanol) and has a melting point of172-174 C.

The structure of 6,14-peroxy-A -dihydroabietic acid, frequently referredto below as levopimaric acid trausannular peroxide, is (11):

17 t I OH;

" "nited States Patent 0 fi CC The preparation of levopimaric acidtransannular peroxide (II), the alkyl esters of (II), and thetransannular peroxides of photosensitized oxidized pine gum may beprepared according to US. Patent No. 2,996,515, issued Aug. 15, 1961.The process involves a photosensitized oxidation whereby pine gum in asolution containing a small amount of a sensitizing dye, such as rosebengal, is simultaneously aerated and irradiated with visible light.

The process of the thermal rearrangement of levopimaric acidtransannular peroxide (II) can be carried out in any suitably inertsolvent, such as toluene, ortho-, meta-, or paraxylene, or mixedxylenes, cumene, pseudocumene, alkylated benzenes of all types, anisole,phenetole, etc. One of the more satisfactory solvents is mixed xyleneshaving a boiling point at about 138 C.

The temperatures at which the thermal rearrangement can be carried outcan be varied from about C. to about 265 C. using an oil bath with apreferable range of about -160 C. At 138 C. the reaction requires about10 hours to go to approximate completion. If higher temperatures areused, shorter heating times are required and, conversely, if lowertemperatures are employed longer reaction periods are necessary forcomplete conversions. It is an advantage of our process that the rateand completeness of the reaction are easily controlled by determiningthe optical rotation [0:]D of the solution.

The concentration of the levopimaric acid transannular peroxide in theinert solvent should generally not exceed 4% as side reactions orsubsequent reactions then become undesirable in amount. A preferableconcentration of the peroxide in mixed xylene for a reaction at about138 C. is about 23%, 2.5%, causing excellent results to be obtained.

Upon completion of the thermal rearrangement of the diepoxide, as can bedetermined by its optical rotation, it can be converted to an aminesalt, e.g., a tertiary butyl amine salt. This is done by the addition ofabout 20% excess of the stoichiometrical amount of a soluble lower alkylamine having one to eight carbon atoms required to react with thediepoxide. The amine salt can then be separated from the solution.

The thermal rearrangement of the alkyl esters of levopimaric acidtransannular peroxide gives products difiering from those obtained bythe thermal rearrangement of the free acid. One product obtained by theprocess using the methyl ester as the starting material has thefollowing properties after one crystallization from aqueous ethanol:M.P. -143" C.; [u] -157 (c. 1.0 in 95% ethanol); no characteristicabsorption from 220320 no peroxide content; A (Nujol mull) 8.06, 11.12,11.45, 1168 essentially no absorption from 220420 1. Such a productforms an embodiment of our invention.

The product of photosensitized oxidized pine gum consists essentially ofa mixture of transannular peroxides from levopimaric acid, palustricacid, and neoabietic acid [cf. J. Am. Chem. Soc, 80, 1438 (1958); ibid.,82, 1734 (1960); ibid, 83, 2563 (1961)]. On heating this photosensitizedoxidized pine gum in an inert solvent, such as mixed xylenes, at about138 C., all of the peroxide content is lost and a product consisting ofa mixture of diepoxides, including the one from levopimaric acidtransannular peroxide is obtained. This mixture of diepoxides is ofconsiderable interest commercially due to its low cost of preparation,being prepared in only two steps from the low-cost, crude, pine gum rawmaterial. The use of this mixture of the diepoxides as additives toasphalt in preparing nonskid surfaces for roads is a demonstrated outletfor a cheap source of such a mixture of diepoxides and is also anembodiment of our invention.

The following examples are set forth by way of illustration only and itwill be understood that the invention is not to be construed as limitedin spirit or in scope by the details therein. Temperatures are given indegrees centigrade. The following abbreviations are employed: M.P. meansmelting point; neut. equiv. is neutral equivalent; n.m.r. (or N.M.R.) isnuclear magnetic resonance expressed as 1- (tau); 95% ethanol means 95%ethanol plus water.

Melting point (M.P.) is determined by means of at Thomas Hoover meltingpoint apparatus; via standard equipment; Infrared A (Nujol mull) viaPerkin-Elmer model 21 infrared spectrophotometer; and n.r.m. by means ofa Varian A-60 spectrophotometer.

EXAMPLE 1 A solution of 2.5 gm. of levopimaric acid transannularperoxide in 125 ml. of mixed xylenes is refluxed at about 138 C. Thereaction is followed by a change in the optical rotation of thesolution. A plot of optical rotation vs. time, levels 011? in abouthours at [ab 49; refluxing is continued for 4 more hours with littlechange in value of [a] The peroxide content is essentially zero in 12hours. A crystalline tertiary butylamine salt of the product is obtainedin 95 yield by weight.

The salt is recrystallized to constant optical rotation fromacetonitrile; yield 2.14 g. (71%); M.P. 183-186 C. decomposes withevolution of gas; 42.7 (c. 0.91 in 95 ethanol); no characteristicabsorption from 220-32Qu; A (Nujol mull) 6.87 (m.), 11.88 (w.), 12.0;1(W.)

Analysis.Calcd. for C H ON: C, 70.7; H, 10.1; N, 3.44; O, 15.7; Neut.Equiv. 408. Found: C, 70.5; H, 10.1; N, 3.65; O, 15.8; Neut. Equiv. 408.

The free acid is liberated from the above salt in 98% yield using dilutephosphoric acid in water. 1.5 g. of the salt is agitated in a solutionof 0.48 ml. conc. phosphoric acid (50% excess) in 50 ml. of water and 50ml. ether. An analytical sample was recrystallized to constant opticalrotation from di-n-propyl ether and then from aqueous methanol; M.P.172174 C. decomposes with evolution of gas; 70.3 (c. 0.80 in 95%ethanol); no characteristic absorption from 220-320 mg; A (Mujol mull)6.92 (shoulder), 8.88 (w.), 11.1 (w.), 11.9 (W.), 12.0 1 (W.).

Analysis.Calcd. for C H O C, 71.8; H, 9.0; O, 19.1; Neut. Equiv. 334.4.Found: C, 71.6; H, 9.2; O, 19.3; Neut. Equiv. 335.5.

EXAMPLE 2 A portion of the free acid of Example 1 is used for thepreparation of the methyl ester by reaction with diazomethane to give apure product of unchanged M.P. on recrystallization from aqueousmethanol; M.P. 121 C.; 72.4 (c. 0.60 in 95 ethanol); no absorption from220-320 mu; A (Nujol mull) 7.0 (m.), 8.04 (s.), 8.82 (m.), 11.07 (m.),11.85 (w.), 11.97 (w.), no hands in 3 2 region; n.m.r. 7:6.99 (1 proton;hydrogen on carbon bearing an oxygen function), a doublet superimposedon a second doublet at about =7.13, 7.23 (total area equivalent to 1proton; a hydrogen on carbon bearing an oxygen function split by twononequivalent adjacent hydrogens).

Analysis.-Calcd. for C H O C, 72.4; H, 9.3; O, 18.4. Found: C, 72.3; H,9.5; O, 18.2.

EXAMPLE 3 A solution of 5 g. of levopimaric acid transannular peroxidein 125 ml. of cumene is held at 138 C. and the reaction is followed bythe change in optical rotation. After a low of [u] 43 at eleven hours,the rotation rises to 41 at twelve hours, whereupon the reaction isstopped and the tertiary-butylamine salt obtained in yield. Afterrecrystallization from acetonitrile the salt is obtained in 60% overallyield (3.66 g.); [a] 43 (0. 1.0 in ethanol).

EXAMPLE 4 A solution of 3.5 g. of levopimaric acid transannular peroxidein ml. of pseudocumene is held at C. in an oil bath. The reaction isfollowed by means of the change in optical rotation. The rotation levelsoff at [111 -50 in about 9 hours, whereupon heating is stopped. Thetertiary-butylamine salt is prepared in 95 yield and recrystallized fromacetonitrile to give 2.77 g. (65%) of pure salt.

Other organic amines including cyclohexylamine, 2-amino-Z-methyl-l-propanol, etc., can be substituted for thetertiary-butylamine.

EXAMPLE 5 A solution of 2.5 g. of levopimaric acid transannular peroxidein 125 ml. of mixed xylenes is refluxed at 138 C. for 12 hours. Therotation is [124L325 49 at this point, and the reaction is stopped. Thetertiary-butylamine salt is prepared in 95 yield by adding 0.93 ml. (20%excess) of tertiary-butylamine and diluting the solution to one literwith pentane. On chilling, 2.89 g. (95 of the salt is obtained. Afterrecrystallization from acetonitrile the salt weighs 1.83 g. (60%); [a]43 (c. 1.0 in 95% ethanol).

EXAMPLE 6 A solution of 2.5 g. of the methyl ester of levopimaric acidtransannular peroxide in 125 ml. of mixed xylenes 1s refluxed at 138 C.The reaction is followed by a change in optical rotation and a decreasein peroxide content. A plot of time vs. optical rotation levels 011? at26 hours at [041 126. The peroxide concentration also levels 011 at thispoint at exactly 50% of the value observed at the start of the reaction.The solvent is stripped off under reduced pressure and the residuecrystallized from aqueousethanol to give 0.34 g. of white crystalshaving the following characteristics: M.P. 135143 C.; [a] 157 (c. 1.0 in95 ethanol); no characteristic absorption from 220-320 m no peroxidecontent; A (Nujol mull) 8.06, 11.12, 11.45, l1.68 essentially noabsorption in 3 region.

EXAMPLE 7 A solution of 5 g. of photosensitized oxidized pine gum(prepared according to U.S. Patent 2,996,515) containing 0.50 equivalentof peroxide/mole of resin acid in 125 ml. of mixed xylenes is refluxedat 138 C. for 12.5 hours at which time all of the peroxide content hasessentially disappeared as determined by titration by means of themethod of Schuller and Lawrence, J. Am. Chem. Soc. 83, 2563 (1961). Thesolvent is removed by stripping under reduced pressure and the residualsyrup is dried in vacuo to give a friable solid which is soluble inethanol, methanol, benzene, and acetone, but insoluble in water andisooctane. Because of its low cost, it is especially useful for additionto asphalts to provide nonskid surfaces on sidewalks and highways.

EXAMPLE 8 A portion of the product of Example 7 is treated by theaddition of 5% of boron-trifluoride etherate (a commercially availableproduct), heating for 10 minutes at 100 C., and then for six hours at160 C. A hard, glossy resin is obtained useful in surface coatings.

We claim:

1. The product prepared by the process of thermally rearranging themixed transannular peroxides resulting from the photosensitizedoxidation of pine gum to give 5 6 the corresponding diepoxides whichprocess comprises the 2,890,209 6/ 1959 Phillips et al. 260-783following operations performed in sequence: 3,112,294 11/ 1963 Newey26078.3 (a) heating the photosensitized oxidized pine gum in 2,996,5158/1961 Moore et a1 260-340.3

an inert organic solvent with stirring to a temperature of about (P4650C OTHER REFERENCES (b) continuing the heating at said temperature until5 Matic 61531-3 Chem- 1953, PP-

the peroxide content is reduced to essentially zero,

(c) removing the solvent by stripping under reduced Agnello 6t Jour-Chem- 0 78 pressure, and pp. 4756 4760.

(d) recovering the thermally rearranged products by 10 Hawklns! OrganicPCI'OXIdeS PP- 243-244,

drying in vacuo. Schuller et 211.: Ind. Eng. Chem., Prod. Res. Develop,

vol. 3, No. 2, June 1964, pp. 97-100. References Cited UNITED STATESPATENTS NORMA S. MILESTONE, Primary Examiner 2,950,289 8/1960Weisenborn. 15 us. c1. X.R. 3,090,792 5/1963 Tyner. 260-2, 348

1. THE PRODUCT PREPARED BY THE PROCESS OF THERMALLY REARRANGING THEMIXED TRANSANNULAR PEROXIDES RESULTING FROM THE PHOTOSENSITIZEDOXIDATION OF PINE GUM TO GIVE THE CORRESPONDING DIEPOXIDES WHICHPROSCESS COMPRISES THE FOLLOWING OPERATIONS PERFORMED IN SEQUENCE: (A)HEATING THE PHOTOSENSITIZED OXIDIZED PINE GUM IN AN INERT ORGANICSOLVENT WITH STIRRING TO A TEMPERATURE OF ABOUT 110*-265*C. (B)CONTAINING THE HEATING AT SAID TEMPERATURE UNTIL THE PEROXIDE CONTENT ISREDUCED TO ESSENTIALLY ZERO, (C) REMOVING THE SOLVENT BY STRIPPING UNDERREDUCED PRESSURED, AND (D) RECOVERING THE THERMALLY REARRANGED PRODUCTSBY DRYING IN VACUO.